Liquid crystal elements are used in mobile equipment such as mobile phone and PDA, display for OA equipment such as copying machine and PC monitor, display for home appliance such as TV, as well as clock, calculator, measuring instrument, automobile instruments, camera, and the like, and the liquid crystal elements are required to fulfill various performances including wide operating temperature range, low operating voltage, high-speed responsivity, and chemical stability.
A material exhibiting liquid crystal phase is used in these liquid crystal elements. Until now, however, the required performances are not realized by one single compound fulfilling all required properties but by way of a liquid crystal composition prepared by mixing two or more liquid crystal compounds or non-liquid crystal compounds each exhibiting one or more excellent properties.
Of the many properties required for the liquid crystal compound used in the liquid crystal composition in the field of the liquid crystal element, it is an important issue to provide a liquid crystal compound or a liquid crystal composition which has excellent compatibility with other liquid crystal material or non-liquid crystal material and improved chemical stability, and which also enables operation of the liquid crystal element at a low voltage with a high-speed responsivity in a wide operating temperature range when used for a liquid crystal element.
As a measure for solving such problem, a compound containing CF═CF linkage group and a compound containing CF2O linkage group have been used (Patent Literatures 1 and 2).
However, the compound containing CF═CF linkage group has the problem of the lack of photostability while the compound containing CF2O linkage group has the problem that the CF2O is decomposed when the compound has particular structures.